Wave guide feed



March 24, 1953 w s c 2,632,852

I WAVE GUIDE FEED Filed Sept. '17, 1945 INVENTOR WILLIAM SICHAK ATTORNEY Patented Mar. 24, 1 953 mesne assignments, to the United States of America as represented by the Secretary ofthe Navy Application September 17, 1945,-Serial N'o. (fl 6,920-

V Claims; 1

My present invention relates in general to'wave' guide means for interchanging electric wavesbetween radio apparatus and free space, and in particular to an open ended wave guide having radiation that is substantially uniformly distributed over the region before the opening.

It is well known that an open ended wave guide will function as anantenna having'abroa'd 1y directional beam pattern at the open end. For example, a rectangular Wave guide may have a beam pattern that is approximately 120 wide, extending 60 each side of the projection of the guide. axis. When it is desired. to feed certain types of reflectors with an open ended wave guide radiator, as for example, a. pill box type or other cylindrical parabolic reflector, with the open ended wave guide located at the principle focus thereof, a beam of 180 width is desirable. A simple open ended wave guide will not produce such a beam and is therefore not suitable as a feed forsuch reflectors.

It is accordinglyan object of my invention to provide an open ended wave guide type antenna which will produce a beam having a width of substantially 180.

It isanother object of my invention to provide such an antenna that will be simple to construct and will not cause undesired reflections or modes of oscillation.

It is a further object of my invention to providev means for broadening the beam of an open ended wave guide antenna which means may be used on wave guides of all sizes without interiering with the normal operation of such wave guides.

My present invention accomplishes the above and other objects by providing at the open end of a Wave guide one or more pairs of oppositely located projections on the walls of the wave guide about the open end, these projections extending substantially longitudinally with respect to the wave guide and forming extensions of selected portions of the walls thereof. The manner in which my invention accomplishes these and other objects and features of my invention will become apparent upon a careful consideration of the following detailed description when taken together with the accompanying drawing, the figures of which illustrate typical embodiments of the invention.

Fig. 1 is a perspective View of an embodiment of my invention;

Fig. 2 is a top view of the apparatus of Fig. 1;

Fig. 3 is a top view of a second embodiment of my invention;

Fig. 4 is a cross secdon along the line'IV- W' of Fig. 3;

Fig. dis a top view ofstill' another embodiment of my invention and Fig. 6 is a cross section along the line V-L-VI of Fig. 5.

Althoughmy invention may be usedi with: any type of wave guide,.l'; preferhereina to: illustrate the principles thereof as embodied in rectangular wave guides. Accordingly inFig. 1,.airectangular waveguide i: havinganopen endi, narrow walls:

3,. and wide" walls 5 has two projections d posi tionea one on each narrowwall. 3 The. projections 4 are each narrower than the wall: 3 on which respectively located, the width not each.

of said projections being substantially one-half;

or slightly less than one-half the. width of a. Walla. Each projection. 4 preferably extends out-- wardly longitudinally withrespect tothe wave guide Iv a distance approximately equal to onehalf the free space wave length of the energy ofprojections 6 similar to the projections- 4' in In. addition. however, a second pairof" Fig. l. projections i are similarly oppositely positioned on the wide walls 5 of the rectangular wave guide I. The first pair of projections 6 preferably extend outwardly from the opening 2 a slightly greater distance than the second pair of projections 1. The respective widths of the projections 6 and I may be determined experimentally to provide the desired beam pattern. In all cases a projection is substantially narrower than the wall on which it is mounted, similarly to the projections 4 in Fig. 1. Each projection may be soldered to the wall of which it forms a partial extension or may be simply an extension of the material of that wall.

Another embodiment of my invention illustrated in Figs. 5 and 6 is similar to the embodiment of Figs. 3 and 4 except that the corners of the rectangular wave guide I are out diagonally rather than rectangularly as in the previous embodiment. This provides pairs of projections 8 and 9, having slanted rather than rectangular edges l0.

Returning now to Figs. 1 and 2 and particularly to Fig. 2, the apparatus of my invention therein illustrated operates to produce a beam having a width of substantially 160 in a plane parallel to a wide wall 5 of the wave guide I, extending substantially 80 on each side of an imaginary projection of the longitudinal axis of said wave guide. The width of this beam is measured at the ten decibel drop point from the peak intensity of the beam. Radiation appears to be centered at a point P which is in the neighborhood of onesixteenth of a wave length in front of the opening 2. This beam extends thus substantially uniformly about the region in front of the opening 2 and is suitable for feeding cylindrical. parabolic reflectors of various types, as for example, of the pill box type. The embodiments of my invention illustrated in Figs. 3 and 6 inclusive operate to produce a beam similar to that produced by the apparatus of Figs. 1 and 2. The additional pair of projections on the wide walls 5 of the wave guide 1 have influence upon the width of the beam pattern in the plane parallel to the narrow walls 3.

The embodiments of my invention herein illustrated are to be regarded as illustrative only and not the only manner in which my invention may be practiced. I prefer that my invention be limited only as necessitated by the prior art and the spirit of the appended claims.

Iclaim:

- 1. Apparatus for the interchange of electric waves between radio equipment and free space comprising, an open ended rectangular wave guide and first and second pairs of oppositely located substantially longitudinally outwardly extending projections mounted on the narrow and wide walls respectively of said wave guide about the open end thereof, each of said projections substantially forming an extension of one of said walls having substantially the same thickness but lesser width than said wall, the projections of said first pair extending outwardly a greater distance than the projections of said second pair.

2. Apparatus for the interchange of electric waves between radio equipment and free space comprising, an open ended rectangular wave guide and a pair of substantially longitudinally outwardly extending conductive projections mounted oppositely on the narrow walls of said wave guide about the open end thereof substantially to form extensions of said walls, said projections being of substantially the same thickness but of lesser width than said walls.

3. Wave guide radiating apparatus comprising, an open ended rectangular wave guide presenting two narrow and two broad walls having an inner conductive surface and first and second pairs of projections oppositely disposed on the narrow and broad walls,wrespectively, of said Wave guide about the open end thereof, each of said projections defining a conductive partial continuation of said inner conductive surface, each of said conductive surface continuations extending outwardly of said open end substantially in the direction of the longitudinal axis of said wave guide, said projections at said narrow walls extending outwardly a greater distance than the projections at said broad walls.

4. Apparatus as defined in claim 3 wherein said conductive surface continuations are rectangular.

5. Wave guide apparatus comprising, a rectangular wave guide having an end apertured in a plane transverse to its longitudinal axis, first and second pairs of projections mounted oppositely at said apertured end on the narrow and broad walls respectively of said wave guide, each of said projections extending outwardly from said apertured end substantially in the direction of the longitudinal axis of said wave guide, each of said projections having uniform trapezoidal transverse cross sections throughout its, longitudinal length, each of said projections having a width that is substantially less than'the width of the wallfrom which it projects.

'WILLIAM SICHAK.

REFERENCES CITED The following references are ofrecord in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,283,935 King May 26, 1942 2,415,807 Barrow Feb. 18, 1947 2,429,640 Mieher Oct. 28, 1947 2,433,368 Johnson Dec. 30, 1947 2,460,109 Southworth Jan. 25, 1949 2,461,005 Southworth Feb. 8, 1949 2,483,575 Cutler Oct. 4, 1949 FOREIGN PATENTS Number Country Date 878,830 France .4 Feb. 4, 1943 

